This invention relates generally to cathode ray tubes (CRT's) used as part of the commonly known test and diagnostic device, the oscilloscope. As electronics technology has advanced, mainly through the development of semiconductor devices, electronic signal processing has gone to higher and higher frequencies in order that more data may be transmitted in shorter periods of time. This is especially true in the computer industry where computer throughput is limited mainly by the access time to semiconductor memories. Electronic engineers and technicians have had at their disposal this very important piece of equipment that is now almost a necessity in many areas of electronic trouble-shooting. Through the use of the oscilloscope and its portraying of the waveforms under observation an actual fault in electronic equipment may be determined in real time by actual observation rather than requiring the engineer to deduce the error from the symptoms displayed by electronic equipment.
The use of the oscilloscope as a test and diagnostic tool is, however, limited by certain inherent features in the oscilloscopes design. Present day oscilloscopes have an adjustable intensity level that is generally manually operated. Because of this singular intensity during the entire oscilloscope trace time, a bright base line on the CRT display will often prevent a transitory signal from being displayed on the CRT in an intelligible manner. This problem is caused by the necessity of increasing the brightness of the base line in order that the transient might be seen. However, if the transient is of short duration with a relatively fast rise and fall time, its display on the screen may be washed out by the brightness of the base line trace. It is to rectify this situation that stimulated the development of the instant invention.